1. Field of the Invention
The present invention relates to an apparatus and a method of modifying surface of polymer powder by rotational ultrasonic treatment, and more particularly, to an apparatus and a method for modifying surface of polymer powder by rotational ultrasonic treatment that pulverize polymer materials, such as rubber, waste rubber, and plastics, and give rotational ultrasonic treatment to the polymer powder to modify its surface, so that the polymer materials can be recycled more efficiently.
2. Description of Related Art
With the rapid development in auto industry, there has been a growing concern on the treatment of waste rubber and waste tires on how to utilize those resources by recycling as well as protecting our environment by doing the same.
However, such efforts had not been successful because of the cost and insufficient technical means developed thus far, and most of them had been either burnt or buried underground, thereby contaminating the environment.
As such, many researchers have been focused on finding effective means for recycling waste rubber and waste tiers, and as a result, there were developed a few methods of chemical treatment using organic solvents and surface treatment by illuminating corona or plasma.
However, waste rubber modified by the above methods is hardly mixed with other materials, and it thus raises problems of physical properties and surface characteristics.
Therefore, a method of modifying waste tires using ultrasonic wave was proposed. This method was first designed by Prelofsky in the 1970s and was refined by Isayev in 1990.
Unlike the radiation technique, the ultrasonic treatment or modification of waste tires using ultrasonic vibration breaks only S—S bonds without affecting C—C bonds. Accordingly, the polymer does not lose its inherent physical properties.
For example, the present inventors submitted an application for a patent about “Method and Apparatus of Surface-Modifying for Waste Rubber using Ozone/Ultrasonic Wave” [Korea Patent Publication No. 2001-0088574(Sep. 28, 2001)]. The apparatus comprises a hopper, an extruder which is linked to the lower part of the hopper and extrudes waste rubber particle and ozone gas flowing into the hopper, an ozone gas outlet which is positioned at one end of the extruder and exhausts the ozone gas, a vacuum pump which is positioned at one end of the ozone gas outlet, a hood which is linked to the vacuum pump and exhausts the ozone gas, an ultrasonic vibrator which is positioned at the end of the extruder and generates ultrasonic wave, a controller that controls the ultrasonic vibrator, and an outlet which discharges the modified powder. This apparatus modifies surface of waste rubber using ozone and ultrasonic wave.
For another example, Korea Patent Publication No. 1995-7002219 (Jun. 19, 1995) discloses “Continuous Ultrasonic Desulfurization of Vulcanized Elastomer”. This patent provides an apparatus comprising: a reactor which has one reactor outlet opening that can continuously feed vulcanized or cross-linked elastomer powder reactor; at least one ultrasonic horn; at least one binding means for binding each ultrasonic horn aligned to the axial direction of the reactor outlet opening; and an ultrasonic wave generator positioned at the end of each ultrasonic horn, which is positioned at a predetermined distance from a transverse plane marking the end of the reactor outlet opening and from a transverse plane marking the tip of the ultrasonic wave generator, whose diameter is larger than that of the reactor outlet opening, and which is sufficient for desulfurization or decrosslinking of the elastomer. The apparatus breaks carbon-sulfur (C—S) bonds, sulfur-sulfur (S—S) bonds, and carbon-carbon (C—C), if necessary, of the vulcanized elastomer.
This surface-modifying apparatus reduces sulfur crossinkage by spatial expansion due to intramolecular pore activation, and improves physical properties of waste tires by ultrasonic surface treatment. Therefore, the binding characteristics and physical properties of waste rubber powder are improved, and thus resources recycling effect becomes substantial.
However, because the ultrasonic treatment was done only at one side of the waste rubber powder in the conventional modification of waste tires, the treatment effect was not good. Moreover, it was not applicable to a large-scale modification.